Update: This article covers removal, see the IE9 Blocker Toolkit from Microsoft to keep it from installing. If you’re looking for registry options, the important values are DoNotAllowIE90 and DoNotOfferIE90 in HKLM\SOFTWARE\Microsoft\Internet Explorer\Setup\9.0.

I’ve had to remove Internet Explorer 9 from a variety of new PCs lately because they’re connecting to online services (hospitals, medical labs, radiology services, etc.) that are not yet compatible with the new version, including issues in Compatibility mode. I’ve also needed to provide instructions (now reproduced here) for some physicians to do the same on home PCs so they can connect into those same systems.

Earlier this week I spent some time troubleshooting a browser-based application that a client is using. The problem cropped up on a PC with a clean install of Windows XP SP3 after assorted system corruption that wasn’t worth the time to repair.

Just ran into this situation after a client uninstalled & reinstalled Office 2007 Pro. When Outlook was opened, it complained twice about being unable to open InfoPath because it wasn’t installed.

I found multiple other complaints about this, but no solutions (though some suggested removing and reinstalling Office). A bit of digging with SysInternals’ Process Monitor, turned up mention of not finding the somewhat promising value “DisableInfopathForms,” so I took a stab and created the value as a DWORD under the location ProcMon was reporting. Setting the value to 1 cleared the problem on Outlook startup.